1. [Field of the Invention]
This invention relates to a sheetlike permeable membrane, a method for the production thereof, and a body fluid filtering apparatus. More particularly, this invention relates to a sheetlike permeable membrane used for dialysis, ultrafiltration, precision filtration, etc., which sheetlike permeable membrane, when it is incorporated in a modular structure, for example, permits ready formation of a stable flow path for a liquid under treatment, a method for the production of the sheetlike permeable membrane, and a body fluid filtering apparatus using the sheetlike permeable membrane.
2. [Description of the Prior Art]
Nowadays various kinds of macromolecular permeable membranes are used in physical and chemical operations of separation such as dialysis, ultrafiltration, and precision filtration, for example. Generally, macromolecular compounds are the most suitable materials for such membranes. Macromolecular permeable membranes, however, are susceptible of deformation. When a sheetlike permeable membrane is incorporated in a modular structure, for example, the deformation renders it difficult for the permeable membrane to retain stably a prescribed flow path for a liquid under treatment.
As a solution for this problem, there has been proposed a sheetlike permeable membrane which, prior to its incorporation in a modular structure such as of a blood plasma separation apparatus, is provided on one surface thereof with a body fluid flow path regulating plate possessed of a jogging surface and which is claimed to form a body fluid flow path in a thickness of high accuracy and manifest a satisfactory ability to separate blood plasma [Japanese Patent Application Unexamined Disclosure SHO 57(1982)-25,857]. In the blood plasma separation apparatus as illustrated in FIG. 11, for example, inside a case comprising cylindrical case proper 54 provided in the central part of the top plate thereof with a body fluid inlet 51, in the peripheral part of the top plate thereof with blood plasma outlets 52, and in the lateral wall thereof with blood fluid outlet 53 and a bottom lid member 56 fitted along the peripheral edge thereof with an O ring 55, a plurality of permeable membrane units 61 each formed by interposing a filtrate flow path forming plate 57 of screen mesh between two vertically opposed sheetlike permeable membranes 50a, 50b, sealing the peripheral edges thereof and the peripheral edge part of a central open part 58, and attaching a sealing material 60 fast to the outer periphery of a filtrate passing hole 59 are superposed as separated by the intervention of a body fluid flow path regulating plate 62 provided with the central open part 58 and the filtrate passing hole 59 opposed to the permeable membrane unit 61 and further provided on the opposed surfaces thereof with a multiplicity of protuberances, and body fluid flow path regulating plates 63 each provided with the central open part 58 and the filtrate passing hole 59 opposed to the permeable membrane unit 61 and further provided on one surface thereof with a multiplicity of protuberances are severally interposed between the upper surface of the uppermost of the permeable membrane units 61 and the upper inner surface of the case and between the lower surface of the lowermost of the permeable membrane units and the bottom inner surface of the case.
In order that the conventional sheetlike permeable membranes may be allowed as described above to form a flow path for a liquid under treatment in a modular structure, for example, it is necessary that mesh plates such as the filtrate flow path forming plates 57 and dotted plates such as the body fluid flow path regulating plates 62, 63 should intervene as spacers between the permeable membranes as in the blood plasma separation apparatus illustrated in FIG. 11. When they are superposed in a multiplicity of layers, therefore, they entail a disadvantage that the modular structure occupies a large space, the assembly of the structure calls for a complicated process, and the priming volume is unduly large.
As a field of utility of the technique of blood plasma separation, the collection of blood plasma from healthy normal person (donor plasma phasis) is attracting attention in these days in addition to the therapy in which the technique has been in popular utility to date. This trend of the technique has been urging development of blood plasma separation apparatuses of smaller dimensions and higher performance.
An attempt at attaining a dimensional reduction in the apparatus proposed as described above requires the thickness of the body fluid flow path regulating plate to be decreased to the fullest possible extent to which the function thereof is not impaired. Because of the limit (approximately 700 to 800 .mu.m) attendant upon the technique available generally today, the dimensional reduction of the apparatus has its own limit. The body fluid flow path in the proposed apparatus mentioned above is formed as interposed between the blood flow path regulating plates 62, 63 and the permeable membranes 50a, 50b as illustrated in FIG. 12. Because of the possibility that the protuberances on the body fluid flow path regulating plate deform the permeable membranes and impart irregularity to the blood flow path as illustrated in FIG. 13, there arises a problem that the permeable membranes are not necessarily allowed to manifest fully the ability of permeation of its own.
An object of this invention, therefore, is to provide a novel sheetlike permeable membrane, a method for the production thereof, and a body fluid filtering apparatus. Another object of this invention is to provide a sheetlike permeable membrane which, on incorporation in a modular structure, permits easy formation of a stable flow path for a liquid under treatment and manifests a distinct ability to filter body fluid and a method for the production thereof. A further object of this invention is to provide a sheetlike permeable membrane which, on incorporation in a modular structure, permits dimensional reduction of modules, simplification of the process of assembly, and reduction in the priming volume, a method for the production thereof, and a body fluid filtering apparatus using the sheetlike permeable membrane.